(a) Field of the Invention
The present invention relates to an automatic gain control apparatus using an efficient receiving structure of an impulse signal-based ultra-wideband wireless communication system, and a method thereof.
(b) Description of the Related Art
In a general wireless communication system, a signal propagated through a transmitting antenna experiences propagation loss in a radio channel. That is, various types of attenuation including attenuation due to a propagation distance, shadow due to a peripheral geographical feature or condition, and multipath delay may occur in a substantial environment. Thus, in order to maintain a stable wireless communication condition in the radio channel environment, a voltage level of a received signal should be maintained in a constant level by using a low noise amplifier (LNA) or a variable gain amplifier (VGA).
Referring to FIG. 1, a structure of a conventional wireless communication receiver based on in-phase and quadrature (I&Q) method will be described.
FIG. 1 shows a conventional wireless communication receiver based on the I&Q method.
Referring to FIG. 1, the conventional I&Q based wireless communication receiver includes an antenna 10 receiving a radio signal, an LNA 20 low-noise-amplifying a gain of the received signal, a local oscillator 50 generating a carrier frequency, a mixer 30 converting the generated carrier frequency to a baseband signal or an IF band signal by multiplying an output signal of the LNA 20 to the carrier frequency, a low pass filter (LPF) or a band pass filter (BPF) 40 filtering the signal output from the mixer 30, a variable gain amplifier (VGA) 60 controlling the gain of the signal, an analog to digital converter (ADC) 70, and a digital signal processing block 80 including an automatic gain controller (AGC) that recovers a signal by using the received signal, and controls an operation range of the received signal by feeding back a gain control voltage to the VGA 60.
The received signal of the conventional wireless communication system is a continuous wave signal having a continuous voltage level. In addition, since a bandwidth of the signal is relatively narrow, the receiver can precisely control a voltage level of the received signal by measuring a received signal strength indication (RSSI).
The automatic gain controller of the digital signal processing block 80 may turn on/off the LNA 20 by measuring an RSSI of the received signal, or may control the RSSI of the received signal to be included within an input range by gain control of the VGA 60. The SNR can be maximized by controlling the receiving signal to have the maximum gain in an operation level of an input terminal of the ADC 70.
However, an ultra wideband (UWB) wireless system based on an impulse signal transmits a transmission signal with a power level that is lower than −41.3 dBm/MHz by using a 2 nS or less pulse due to the spectrum mask specification. In addition, due to a transmission signal characteristics of generating a discrete impulse rather than a continuous impulse, it may be difficult to determine whether there is a transmission signal at a remote distance. Due to these factors, errors in RSSI-based signal detection of received signals increase, and accordingly automatic gain controller performance using the RSSI deteriorates receiving performance.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.